Add the ctick command

[xpple]

This PR adds a simple ctick command for querying both the client's and server's TPS and MSPT. The expected value is printed for completeness. The task code is mostly copied from:

clientcommands/src/main/java/net/earthcomputer/clientcommands/command/CommandTick.java

Lines 175 to 255 in c1e3766

	private static class TickMeasuringTask extends LongTask {
	private static final int PERIOD = 100;
	private int tickCount = 0;
	private long totalTickTime = 0;
	private long startTickTime;
	private boolean hadFirstTick = false;
	private long firstTickStart;
	private long lastTickStart;
	private ICommandSender sender;
	private boolean tps;
	private boolean forceInaccurate;
	public TickMeasuringTask(ICommandSender sender, boolean tps, boolean forceInaccurate) {
	this.sender = sender;
	this.tps = tps;
	this.forceInaccurate = forceInaccurate;
	}
	public void incrTickCount(int count) {
	if (!hadFirstTick) {
	firstTickStart = System.nanoTime();
	hadFirstTick = true;
	} else {
	tickCount += count;
	}
	}
	public void startTick() {
	startTickTime = System.nanoTime();
	if (!hadFirstTick) {
	firstTickStart = startTickTime;
	hadFirstTick = true;
	}
	}
	public void endTick() {
	if (hadFirstTick) {
	totalTickTime += System.nanoTime() - startTickTime;
	tickCount++;
	}
	}
	@Override
	protected void taskTick() {
	if (tickCount >= PERIOD) {
	lastTickStart = System.nanoTime();
	setFinished();
	}
	}
	@Override
	public void start() {
	sender.sendMessage(new TextComponentTranslation("commands.ctick.measuring"));
	}
	@Override
	public void cleanup() {
	if (tps) {
	long totalTime = lastTickStart - firstTickStart;
	double tps = 1000000000D * tickCount / totalTime;
	sender.sendMessage(new TextComponentTranslation("commands.ctick.tps",
	totalTime == 0 ? "Immeasurable" : DEC_FMT.format(tps)));
	} else if (forceInaccurate) {
	long totalTime = lastTickStart - firstTickStart;
	double mspt = totalTime / (1000000D * tickCount);
	sender.sendMessage(new TextComponentTranslation("commands.ctick.mspt", DEC_FMT.format(mspt)));
	sender.sendMessage(new TextComponentTranslation("commands.ctick.mspt.inaccurate"));
	} else {
	double mspt = totalTickTime / (1000000D * tickCount);
	sender.sendMessage(new TextComponentTranslation("commands.ctick.mspt", DEC_FMT.format(mspt)));
	}
	}
	@Override
	public int getTimeout() {
	return 1200;
	}
	}